Slow Aggregation MongoDB - mongodb

Question

My Aggregation is pretty slow. I've already made it a little faster (from 3000 ms to 200ms) by using the match statement before the unwind statement. Is there any other way to improve my aggregation? In the end there'll be just one result (the last one based on timestamp). The unwind part is the longest operation if i'm right yet i really do need this.
db.CpuInfo.aggregate([
{"$match":
{
"timestamp": {"$gte":1464764400},
'hostname': 'baklap4'
}
},
{ "$unwind": "$cpuList" },
{ "$group":
{ "_id":
{ "interval":
{ "$subtract": [
"$timestamp",
{ "$mod": [ "$timestamp", 60 * 5 ] }
]}
},
"avgCPULoad": { "$avg": "$cpuList.load" },
"timestamp": { "$max": "$timestamp" }
}
},
{ "$project": { "_id": 0, "avgCPULoad": 1, "timestamp": 1 } },
{$sort: {'timestamp': -1}},
{$limit: 1}
])
The items in my collection are all simular to this:
{
"_id": ObjectId("574d6175da461e77030041b7"),
"hostname": "VPS",
"timestamp": NumberLong(1460040691),
"cpuCores": NumberLong(2),
"cpuList": [
{
"name": "cpu1",
"load": 3.4
},
{
"name": "cpu2",
"load": 0.7
}
]
}
I've added the explain option to my aggregation and this is the result:
{
"waitedMS" : NumberLong(0),
"stages" : [
{
"$cursor" : {
"query" : {
"timestamp" : {
"$gte" : 1464732000
},
"hostname" : "baklap4"
},
"fields" : {
"cpuList" : 1,
"timestamp" : 1,
"_id" : 0
},
"queryPlanner" : {
"plannerVersion" : 1,
"namespace" : "prototyping.CpuInfo",
"indexFilterSet" : false,
"parsedQuery" : {
"$and" : [
{
"hostname" : {
"$eq" : "baklap4"
}
},
{
"timestamp" : {
"$gte" : 1464732000
}
}
]
},
"winningPlan" : {
"stage" : "FETCH",
"filter" : {
"hostname" : {
"$eq" : "baklap4"
}
},
"inputStage" : {
"stage" : "IXSCAN",
"keyPattern" : {
"timestamp" : NumberLong(1)
},
"indexName" : "timestamp_1",
"isMultiKey" : false,
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 1,
"direction" : "forward",
"indexBounds" : {
"timestamp" : [
"[1464732000.0, inf.0]"
]
}
}
},
"rejectedPlans" : [ ]
}
}
},
{
"$unwind" : {
"path" : "$cpuList"
}
},
{
"$group" : {
"_id" : {
"interval" : {
"$subtract" : [
"$timestamp",
{
"$mod" : [
"$timestamp",
{
"$const" : 300
}
]
}
]
}
},
"avgCPULoad" : {
"$avg" : "$cpuList.load"
},
"timestamp" : {
"$max" : "$timestamp"
}
}
},
{
"$project" : {
"_id" : false,
"timestamp" : true,
"avgCPULoad" : true
}
},
{
"$sort" : {
"sortKey" : {
"timestamp" : -1
},
"limit" : NumberLong(1)
}
}
],
"ok" : 1
}
When i Look up in my table i see that Timestamp and Id are indexed:
db.CpuInfo.getIndexes()
[
{
"v" : 1,
"key" : {
"_id" : 1
},
"name" : "_id_",
"ns" : "prototyping.CpuInfo"
},
{
"v" : 1,
"key" : {
"timestamp" : NumberLong(1)
},
"name" : "timestamp_1",
"ns" : "prototyping.CpuInfo",
"sparse" : false
}
]